Electrical apparatus



July 2, 1946. .1. F. KovALsKY ELECTRICAL APPARATUS lllL Filed 00hs-.720,1942 l l /.g//a .4521925 IW. M. Wam?? WITNESSES:

Patented July 2, 194e UNITED STATES PATENT OFFICE ELECTRICAL APPARATUSJoseph F. Kovalsky, Turtle Creek, Pa., assigner to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication October 30, 1942, Serial No. 463,979

(Cl. ZOO-104) 2 Claims. 1 This invention relates to electrical apparatusand, particularly, to the circuit' controlling devices of regulators ofthe rheostatic type.

In the known circiut controlling devices of the rheostatic type andparticularly those including a large number of spring biased contactAinembers for shunting successive sections of a resistor, an elongatedarmature member responsive to a change in an electric quantity isgenerally used to actuate the contact members. Usually the elongatedarmature member is pivotally mounted on thin leaf springs of one form orthe other in order to provide a substantially floating pivot.

Where the Spring pvot for the armature member is of the cross-springtype, that is, two thin leaf springs in the horizontal position and twothin leaf springs in the vertical position to form a frictionless pivotalong the line of intersection of the cross springs, it is foundthatinVcertain applications, the springs bend or buckle and prevent properoperation of the regulator. This is particularly true in applicationswhere the voltage swings to a high value or where `thee-regulatorfissubjected" to high impact shocks as in navy applications.

In order to prevent such bending or buckling, it is necessary to useAheavier leaf springs of the order of .012 to .D20 inch thick, ascompared to the thinner springs having a thickness of .008 to .010 inch.With such heavier springs, it is found that the performance of theregulator is affected, the sensitivity is reduced, and that it isimpossible to correct the unbalanced condition by adjustments in theexisting component parts of the regulator. l

.It is an object of this invention to provide in a regulator a circuitcontrolling device capable of withstanding physical shock and having ahigh degree of sensitivity.

Another object of this invention is to provide in a regulator a circuitcontrolling device having Substantially balanced forces for obtaining ahigh degree of sensitivity in the operation thereof.

Other objects of this invention will become apparent when taken inconjunction with the accompanying drawing, in which:

Figure 1 is adiagrammatic view illustratingv circuits and apparatusembodying the teachings of this invention;

Fig. 2 is a front elevational'view of a regulator embodying theteachings of this invention;

Fig. 3 is a graph, the curves of which illustrate certain of the forcesapplied during a movement of the circuit controlling device Fig. 4 is agraph, `the curves of which also illustrate certain of the forcesapplied during movement of the circuit controlling device; and

Fig. 5 is a graph, the curves of which are representative of thesensitivity of the regulator, y

Referring to Figure 1, a circuit controlling device constructed inaccordance with this invention is illustrated as disposed forcontrolling the voltage of a generator I0. The generator I0 is providedwith an armature winding I2 connected to supply current to circuitconductors I4 and I6 and a shunt field winding I8. The shunt iieldwinding I8 is connected at one end to the armature winding I2, the otherend being connected through an adjustable rheostat 20 and a regulatorresistor 22 to the other terminal of the armature l2.

A rheostat controlling element including a plurality of elongatedconducting leaf springs 24 arranged in a stack and so mounted at oneendl that their Xed ends are insulated from each other and-connectedbyconductors 26 to different points along the resistor 22 is disposed for-controlling the number of sections of the resistor which are connectedin circuit with the field winding I8. The other endsfof the leafsprings24 carry cooperating contact members (not shown) and are free to move inone direction, being self-biased in the other direction towards thesloped stop 2B of `insulating material which functions to separate thesprings 24 and contact members carried thereby when seated thereagainst.

A driving member 30 of insulating material is carried by a movable arm32 and is so disposed to actuate the Springs 24 into progressiveengagement to sequentially shunt the sections of resistor 22. Asillustrated, the movable arm 32 is pivotally mounted by a plurality ofcross springs 34 and 36, two of each being provided on the corestructure 38 of an electromagnet 40, the armature 42 of which is carriedat the lower end of the arm.

In assembling the movable arm 32, a'bracke 44 is secured to the arm,spaced vertical surfaces being provided thereon for receiving the uppernends of the spaced vertical springs 36 and spaced horizontal surfacesare provided for receiving one of the ends of the spaced horizontalsprings 34. A supporting bracket 46 is secured to the core structure 38,as illustrated in Figs. 1 and 2, a part of the bracket being cut away inFig. l to illustrate the assembly of the component parts. The bracket 46is also provided with spaced horizontal surfaces for receiving one endof the horizontal springs 34 and spaced vertical surfaces for 3receiving the lower ends of the vertical springs 36. When the ends ofthe horizontal and vertical springs 34 and 36, respectively, are mountedand secured to the brackets 44 and 46, as described hereinbefore, theline of intersection of the planes of the springs constitutes africtionless pivot for the arm 32.

The electromagnet 40 having the core member 38 identified hereinbeforeis provided with an energizing winding 48, the armature member 42carried by the movable arm 32 being disposed for movement in the air gapformed in the core member as the energization of the winding'4`8changes. The armature 42 is preferably tapered as illustrated so that asthe armature moves in the air gap of the core member 38 in response toan increase in the energization of the winding 48, the width of thearmature from top to bottom Within the air gap will increase to effectan increase in the magnetic pull on the armature.

In order to actuate the movable arm 32 to opcrate the springs 24 tocircuit closing position under certain conditions, a main coil .spring52 is provided having one end secured to the arm 32 and the other endsecured to an adjustable bolt 54. The adjustable bolt 54 is carried by abracket 56 which is secured to the core member 38 as illustrated. Thepull of the spring member 52, the force of the leaf springs 24, and thetaper of the armature 42 are so adjusted that the sum of the forces ofthe springs 24 and 52 for any position of the armature 42 within theregulating limits of travel is substantially balanced .by the magneticpull within the same limits of travel so that the positioning of thearmature and, consequently, the positioning of the driver member 30 aredetermined by the degree of energization of the winding 48.

However, since the cross springs 34 and 36 forming the pivot for the arm32 are made of, relatively heavy material in order to prevent bending orbuckling of the springs, they exert. a force which upsets the balancebetween the Spring forces and magnetic pull required for sensitiveoperationv of the apparatus. As mounted the cross springs `34 and 36have a zero bias on the movable arm 32 for some intermediate pointbetween the limits of movement of the arm for the regulatini;` limits oftravel, as illustrated by the curve` 58 of Fig. 3, but dependent uponthe point at which balance is to be maintained. The zero bias point isusually selected to be near the open circuit position of the leafvspring assembly. The curve 60 of Fig. 3 is representative of the forceo1 the leaf springs 24 of the stack as the 'stack is operated from anopen to a closed position for the contact member, whereas curve 62 isillustrative o! the unbalanced condition resulting from the use of theheavy cross springs 34 and 36. It ls evident that with the heaviercross-spring pivot that the slope of the lcomposite forces of thesprings represented by curve 62 is quite steep over theregulating limitsof travel.

In order to offset the change in the bal-ance of the forces where theheavier springs 34 and 36 are employed, an auxiliary elongated leafspring 64 is secured at one of its ends to one side of the movable arm32 at its lower end by `any suitable means, such as the bolt 66 and nuts68. A projecting lug l is also provided at the lower end of the erm 32,'the bolt 66 projecting through the lug 18, the arm 32, and the spring64 to maintain them integral. As illustrated, the lug 'I3 and Spring j64are provided` with a slot 132 and T4, respectively, to fit over the bolt'I6 which is adjustably mounted on a stop 18. The stop 18 is secured tothe panel 80, as illustrated in Fig. 2, and is disposed to be engaged bythe lug 'I0 to limit the movement of the arm 32 in a clockwisedirection, as illustrated in the drawing.

By adjusting the nut on the bolt 16, the force of the spring 64 may bevaried, it being noted that when the lug 10 is seated` against the stop18 and the spring `64 is free from the nut on the bolt I6 that thespring 64 has a zero bias, and that when the spring 64 i's seatedagainst the nut on the bolt 'I6 by a movement of the arm 32 in acounterclockwise direction about the cross-spring pivot that the spring64 has a maximum bias. The spring 64 thus opposes the force of thecrossspring pivot over the major part of the travel of the movable armto the circuit closing position.

A representation of the eiect of the spring 64 is made in Fig. 4 inwhich curve 62 represents the combined force of the leaf springs 24 andthe cross springs 34 and 36 as the movable arm pivots to actuate thesprings 24 from an open circuit position to a circuit closing position.Curve 82 is representative of the force of the auxiliary leaf spring 64over the same distance of travel, and curve 84 is representative of thecombined forces of the springs 24, 34, 36, and 64. As illustrated, theresultant curve 84 is not as steep as curve 62 with the result that agreater degree of sensitivity in response to a change in theenergization o1' coil or winding 48 is effected.

As illustrated in Fig. l., `the winding 48 of the electromagnet 40 isconnected across the generator I0, one terminal of the winding 48 beingconnected by a conductor 86 through an adjustable resistor 88 andconductor 90 to one side of the armature winding I2, and the otherterminal of the winding 48 being connected by conductor 92 through theprimary Winding 94 of a stabilizing transformer to conductor I6. Thewinding 94 of the stabilizing transformer is inductively coupled to awinding 96 that is connected across the shunt field winding I8 of thegenerator.

In operation with the regulator constructed as described, when thegenerator II) is started and the voltage applied `between conductors I4and I6 is below the required value, then the energize.- tion of thewinding 48 of the electromagnet is correspondingly decreased. The forceof the main spring 52 `being larger than the restraining magnetic pullon the armature 42 effects a movement of the arm 32 in a clockwisedirection about the cross-spring pivot to actuate the leaf springs 24away from the sloped stop 28 into circuit clos ing engagement tosequentially shunt additional sections of resistor 22 from the fieldcircuit. By thus shunting sections of the resistor 22, the energizationof the field winding I8 is increased with the result that the voltageacross conductors I4 and I6 is increased.

Likewise if the voltage applied between conductors I4 and I 6 isincreased, the enengizatlon of the winding 48 is increased with theresult that a stronger magnetic pull is applied to the armature 42 toactua-te the arm 32 in a counterclockwise direction to sequentially openthe circuit between the leaf springs 24 and connect additional sectionsof the resistor` 22 in the field circuit. This reduces the energizationof the field I8 with the result that the voltage across conductors II4and I6 decreases to the required value.

Itis to be noted that with the contacts of the spring leaf members 24 inthe open position that the cross-spring vpivots 34 and 36 have anegative bias, as represented by curve 58 of Fig. 3, tending to opposethe magnetic pull on the armature 42. It is also noted that, as shown bycurve 82 of Fig. 4, the leaf spring member 64 has a positive biastending to actuate the leaf spring members 24 to their circuit closingposition. As the arm 32 moves in the clockwise direction as the magneticpull is decreased, the bias of the crossspring pivots 34 and 36 passesthrough a Zero point and becomes an increasing positive force, While thebias of the leaf spring 64 becomes decreasingly small but opposes theincreasing force of the pivot over the range of movement of the arm 32.By this arrangement, the forces of the springs cooperate, giving aresultant curve of changing force over the range of travel of the arm32, as represented by curve 84 of Fig. 4, whereby the arm 32 isresponsive to slight changes in the energization of the winding 48 ofelectromagnet 4|! giving a substantially nat Working range, asrepresented by the curve 98 of Fig. 5, the dotted curves |00 and |02representing a range which may be obtained by adjusting the bolt 15. Thecurve |04 of Fig. 5 represents the type of sensitivity response of thecircuit controlling device to a chan-ge from the energization of theWinding 48 Where the auxiliary leaf spring member 64 is not present.

By providing the spring member 64 as described hereinbefore, it isreadily apparent that the unbalanced condition of the forces of thespring members which occurs when the cross springs 34 and 36 are made ofheavier material are substantially compensated, and that the controllingdevice is quite sensitive to changes in voltage. Thus, a circuitcontrolling device is provided which, while being able to withstand highimpact shocks, has an overall sensitivity comparable to the circuitcontrolling devices produced hereinbefore.

Although this invention has been described with reference to aparticular embodiment thereof, it is, of course, not to be limitedthereto eX- cept insofar as is necessitated by the scope of the appendedclaims.

I claim as my invention:

1. In a regulator for controlling an electric quantity over apredetermined Working range, a control device comprising, a plurality ofcontact members disposed to be actuated in sequence, a member disposedto actuate the contact members, a cross-spring pivot for the actuatingmember, a biasing means secured to the member to effect a non-linearpull thereon to actuate the member in one direction about its pivot,electroresponsive means disposed to be energized for actuating themember in the opposite direction about its pivot, a stop means disposedadjacent the actuating member to limit the movement thereof in the oneor opposite directions, and a spring means carried by the actuatingmember, the spring means having a free end disposed for movement betweenthe limits of the stop means whereby the spring means is free from biaswhen actuated the limit in the one direction and engages the stop meanswhen actuated in the oppO- site direction to apply a compensating forceto the actuating member to render the actuating member sensitive to achange in the energization of the electro-responsive means.

2. In a regulator for controlling an electric quantity over apredetermined Working range, a control device comprising, a plurality ofcontact members disposed to be actuated in sequence, a member disposedto actuate the contact members, a cross-spring pivot for the actuatingmember, a biasing means secured to the member to effect a non-linearpull thereon to actuate the member in one direction about its pivot,electro-responsive means disposed to be energized for actuating themember in the opposite direction about its pivot, the cross-spring pivotbeing disposed to have a zero bias on the actuating member at someintermediate point between the limits of movement in said one andopposite directions, the cross-spring pivot thereby applying a biasingforce to oppose movement of the actuating member as it approaches thelimit of movement of said member in either of said one or the oppositedirections, a stop means disposed adjacent the actuating member to limitthe movement thereof in said one or opposite directions, and anelongated leaf spring carried by the actuating member, the leaf springhaving a free end disposed for movement between the limits of the stopmeans whereby the leaf spring is free from bias when actuated the limitin the one direction and engages the stop means When actuated in theopposite direction to apply a force to the actuating member to opposethe movement of the actuating member in said opposite direction.

JOSEPH F. KOVALSKY.

